Fire trucks, fire boats, military equipment, and stationary fire suppression systems are used to extinguish large industrial fires and will typically have water discharge lines coupled to a large capacity pump where the discharge lines vary in size from those feeding a water cannon capable of delivering over 1,000 gallons per minute to hand lines used in mopping-up operations that may deliver under 20 gallons per minute.
One of the most significant advancements in the field of fire fighting has come through the use of chemical foamants specifically formulated to augment the fire fighting ability of water. Foam injection systems have been designed to introduce liquid chemical foamant concentrate into a water stream being directed at a fire. A key advantage to using such foams is the dramatic reduction in the time required to extinguish fires. It has been demonstrated that Class A foam is from five to ten more times more effective as a fire suppressant than water alone. Utilizing foam, fires are extinguished faster and with substantially less water damage. The foam proves to be an effective barrier, preventing fire from spreading and protecting adjacent structures. As is set out in the U.S. Reissue Pat. No. 35,362 issued to Arvidson et al. (“the Arvidson Reissue patent”), the teachings of which are hereby incorporated by reference, it is desirable to have a foam injection system that is capable of automatically proportioning the foam additive in the concentration required for the specific fire-fighting problem. The Arvidson Reissue patent describes a system that is readily suited to residential fires, automobile fires, and those applications, where water flow rates tend to be below 1,000 gallons-per-minute.